(1) Field of the Invention
The present invention relates to a homokinetic articulated transmission joint, termed a telescopic or sliding joint, of the type employed in lateral or longitudinal transmissions of vehicles having a front wheel drive, or propelled by independent wheels, or having four driving wheels. The present invention concerns more particularly a telescopic transmission joint, in particular for a vehicle, comprising a first element provided with three arms disposed substantially radially relative to its axis and each partly surrounded by two roller segments whose radially outer surfaces, in the form of sections of a torus, are in rolling contact with longitudinal rolling tracks on a second element, which tracks have in cross-section a direction of curvature which is complementary to that of the radially outer surfaces of the roller segments.
(2) Description of the Prior Art
As is known, it is attempted to avoid in automobile vehicles having an internal combustion engine, that the vibrations of the engine be transmitted to the structure and the compartment of the vehicle. In particular, the transmission shafts which transmit the power of the engine to the wheels, and consequently have a notable rigid mass, should in no way transmit vibrations from the engine to the structure through the hubs of the driving wheels.
For an even stronger reason, the operation of these transmission shafts must in no case itself produce vibrations.
There is known from the patent FR-A-2 525 306 a joint of the type indicated at the beginning of the description in which the arms of the first element, namely a tripod element, bear against an inner cylindrical surface of the roller segments through a bush with interposition of needles between the bush and the segment. The bush is in itself free to pivot on the arms of the tripod element about an axis perpendicular to the axis of the tripod element and to the radial direction of the considered arm.
Such a joint is extremely complex. While it certainly minimizes the relative sliding movements between all the pairs of parts, these movements have direction changing points or stoppage points which produce vibrations.
There is also known from the patent FR-A-2 580 751 a joint in which the arms of the first element are shaped in spherical regions in swivelling contact with bars bearing in the rolling tracks through balls mounted in cages. Here again, the number of parts is relatively large and their stacking considerably increases the volume of the barrel, the weight, the cost and the overall size of the joint.